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Name ______________________
Period _______
Chapter 4: Atomic Structure
Atomic Theories
Greeks:
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Dalton’s Atomic Theory
All elements are composed of _____________________indivisible
particles called_____________.
Atoms of the same element are_________________. Atoms of
different elements are __________________.
Atoms of different elements can _________________mix together or ___________________ combine.
Chemical reactions occur when atoms are__________________,
_________________, or _________________________.
J.J. Thomson
English physicist discovered electrons in 1897.
Experimented with flow of electron current through gases.
Electrodes connected to high energy electricity source.
Positive side – _______________
Negative side- _______________
Cathode ray – glowing beam, which travels from the cathode to the
anode.
Thomson proposed that the cathode ray had a stream of small
negatively charged particles.
Plum Pudding Theory – Electrons are imbedded in a positive sphere.
Robert A. Millikan
American
Calculated by 1916 that the electron had one unit of negative
charge and mass is 1/1840 the mass of Hydrogen atom.
Sir James Chadwick
Subatomic particles with no charge –_____________
Mass is nearly equal to that of the _____________
Subatomic Particles
Particle
charge
relat.mass
mass
Proton (p+)
Neutron (n0)
Electron (e-)
Ernest Rutherford
1911 – Gold Foil Experiment
Proposed that almost all of the ________ and all the _____________
charge are concentrated in a small region at the center of the atom
called the_______________.
Nucleus- the central core of the atom, composed of protons and
neutrons.
The Development of Atomic Models
Dalton’s Atomic Model –
Thomson’s Model –
Rutherford’s Model – Positive dense tiny ______________ is
surrounded by ________________ in empty space.
Neils Bohr – 1913, Danish physicist
Planetary Model
Electrons have a fixed path.
Erwin Schrodinger – 1926
Quantum Mechanical Model – the modern description of the electrons
in the atoms comes from the mathematical solution to the Schrodinger
equation.
Electron Cloud (_________________________)
Atom
Atom – smallest part of an element that retains the _______________________
Atomic Theory – proposed by John Dalton.
Elements are ____________________________
Compounds are _______________________________
Subatomic Particles
___________________ negatively charged particle,
has almost no mass.
___________________ positively charged particle,
relatively heavy.
___________________ particle with no charge,
relatively heavy.
mass of ______________ = mass of ______________
Structure of the Atom
Nucleus
Negatively charged electrons move around the nucleus.
 only _____________ electrons involved in forming chemical
bonds.
most of atom is__________ __________.
Atomic Number
Atoms are _________________ which means _________.
Ions are
______________which means
___________________________________.
Mass Number
The approximate ________ of an atom of an______________.
Mass # =
 Sum of the mass of __________particles
Amu –
1 amu =
1/12 the mass of a Carbon atom with 6p+ & 6no
# neutrons =
Isotopes
Atoms that have the same ____________________________but
different______________________________.
 Therefore they have different____________ ________.
 Different isotopes of an ____________ are chemically__________.
 When you round the atomic mass on the Periodic Table, you get
the mass # of the most _______________________________of the
element.
Isotopes are ___________ which means ____________.
ONLY the number of ________________ changes.
Example:
He
or may be written as He-4
Note: The number of protons never changes; it is the number
of protons that determines what element an atom is.
Atomic Mass
Found on the Periodic Table
 It is the _____________ ______________ of the masses of all the
naturally occurring isotopes of that element.
_________________________________is the weighted
average of the masses of all the isotopes of an element.
____________________________is the total number of protons
and neutrons in one atom of an element.
Calculation of average atomic mass.
For Element “X”
isotopes
x – 10
x – 11
mass #
10
11
abundance
20% = .20
80% = .80
10X (10)(.20) = 2.0
11X (11)(.80) = 8.8
10.8 amu
You Try Copper (Cu)
For Copper
isotopes
Cu-63
Cu-65
mass #
63
65
abundance
69.1%
30.9%